1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for scheduling for collaborative spatial multiplexing (CSM) in a broadband wireless communication system.
2. Description of the Related Art
It is important to efficiently use limited radio resources in a wireless communication system. A multi-input multi-output (MIMO) scheme is one scheme for efficiently using the limited radio resources. The MIMO scheme spatially divides communication channels using a plurality of transmitting (TX) antennas and receiving (RX) antennas. Because a MIMO communication system transmits/receives different signals by spatially dividing channels of N antennas while using the same time resource and the same frequency resource, it can provide up to N times the channel capacity gain of a single-antenna system.
A collaborative spatial multiplexing (CSM) scheme has been proposed as an application of the MIMO scheme. The CSM scheme constructs a virtual MIMO environment for uplink communication by treating a plurality of mobile stations (MSs) as one MS using a plurality of antennas. That is, when a plurality of MSs simultaneously transmit signals to a base station (BS) with a plurality of RX antennas through the same resource region, the BS detects the signals from the respective MSs according to the MIMO scheme.
FIG. 1 illustrates BSs and MSs that perform communications in a broadband wireless communication system by using a CSM scheme.
Referring to FIG. 1, a first BS 110-1 performs uplink communication with a first MS 120-1, a second MS 120-2, and a third MS 120-3. The first MS 120-1 and the third MS 120-3 transmit signals by both using a resource A, while the second MS 120-2 transmits a signal by using resource B. That is, the first MS 120-1 and the third MS 120-3 perform uplink communications by using the CSM scheme.
The signal transmitted from the MSs 120-1 and 120-3 to the first BS 110-1 acts as an interference signal to a second BS 110-2 of a neighboring cell. Because the second MS 120-2 monopolizes resource B, the signal transmitted from the second MS 120-2 does not act as a strong interference against the second BS 110-2. However, because the MSs 120-1 and 120-3 both use resource A, the sum of the signals transmitted from the MSs 120-1 and 120-3 acts as a strong interference to the second BS 110-2.
Therefore, a need exits for a scheme for reducing the interference resulting from the CSM scheme.